I wouldn't say that other systems are behind Wordpress because every system out there caters to different markets. Wordpress is popular simply because it was one of the first of the kind to offer blogging for average users. In a way where it takes very little to no technical skills to set-up a blog. Especially when one uses the hosted Wordpress service. There is little to no technical investment when setting up a blog in that way. Everyone and their brother wants to heard via a blog. Hence, why Wordpress became so popular.
Than somewhere down the line people became so reliant on Wordpress that they began to turn it into things it wasn't really meant for like stores, business directories, etc. I really think that just comes down to ignorance and an unwillingness, incapability to use other software.
it is important to point out that Wordpress from a technical standaoint is built like this building in Bangladesh. The reason why it is so popular is timing, marketing and ease of use for none-technical users.
If anything is behind the times it is Wordpress. The architecture of Wordpress hasn't changed very much since it was first conceived. Still there isn't debating it is a popular platform. From a none-technical stand-point I undertand why it is but from a technical one, coming from someone who appreciates innovative, modern software solutions it is not.
I myself find it hard to take anyone seriously in the technical realm who bows down to Wordpress for any and all projects. People like that in my opinion don't care one bit about matching up proper software solutions to real world business problems. Those people are just simply hooked on Wordpress like cocaine or any other drug. I see it all around, especially in this very forum and it makes me sick. People selling Wordpress as the optimal eCommerce package out there… give me a break. Try placing millions of products in that serialized database and see how great you're system is than.